<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>

    <!--外边距的妙用：居中元素
     margin: 0 auto;
    -->
    <style>

        #box{
            width: 300px;
            border: 1px solid red;
            margin: 0 auto;
        }
        /*
        顺时针旋转
        margin:0
        margin:0 1px
        margin:0 1px  2px   3px

        */
        h2{
            font-size: 16px;
            background-color: #3cbda6;
            line-height: 30px;
            color: white;
            margin:0 1px 2px 3px;
        }

        form{
            background: #3cbda6;
        }
        input{
            border: 1px solid black;
        }
        div:nth-of-type(1){
            padding: 10px 2px;
        }
    </style>

</head>
<body>


<div id="box">
    <h2>会员登录</h2>
    <form action="#">
        <div>
            <span>用户名：</span>
            <input type="text">
        </div>
        <div>
            <span>密码：</span>
            <input type="text">
        </div>
        <div>
            <span>邮箱：</span>
            <input type="text">
        </div>

    </form>
</div>

<img src="images/tx.jpg" alt="" style="margin: 0 auto">


</body>
</html>